Just a Suggestion. If you work mainly of Mains, do not fit the battery. Only when you go on the road fit the battery as, when you are running of mains and the battery installed the battery is on charge all the time. This shortens the life of the battery, Laptop builders are now changing that so they run of battery till the charge drops to a certain level before the charger kicks in. If you are in the house charge the battery to about 40% put in a plastic bag and put on the middle shelf of your fridge, this will save it from running down as fast.
That's what I do with mine, at £155 a go I do not relish keep paying out that amount